Arrangement for the automatic interrupting of the net circuit of multiphase motors



2 Sheets-Sheet l Apnl 14, 1931- G. "KELLER ARRANGEMENT FOR THE AUTOMATIC INTERRUPTING OF THE NET CIRCUIT OF -MULTIPHASE MOTORS Filed Jan. '18, 1927 //7 l enlor:

April 14, 1931. ca. KELLER 1,300,256 ARRANGEMENT FOR THE AUTOMATIC INTERRUPTING OF THE NET CIRCUIT OF MULTIPHASE MQTORS Filed Jan. 18, 1927 2 sheets -sheef. 2

Patented Apr. 14, 1931 UNITED STATES GEORG KELLER, OF GORLITZ,

GERMANY, ASSIGNOR GORLITZ, GERMANY PATENT OFFICE,-

TO FIRM PAUL STROBAOH, OF

ARRANGEMENT FOR THE AUTOMATIC IN TERRUPTING OF THE NET CIRCUIT OF MULTI- PHASE MOTORS Application filed January 18, 1927, Serial No.'161,892, and in Germany March 24,1926.

Safety-switches for multiphase currents for protecting machines connected to such lines, as motors or the like, which function immediately at the failing of the current in one phase, have become known. In these arrangements a solenoid is inserted in each phase-wire, the core of said solenoid carrying the movable contacts of switches inserted in the circuit of another solenoid. The core of this second solenoid effects, when being moved at the excitation of the solenoid, the releasing of va mechanical locking, which holds in the closing position a switch arranged in front of the motor to be protected.

When the current fails in one phase, the corresponding phase-solenoid becomes ourrentless and its core closes the circuit of the protecting solenoid so that the releasing of the looking and consequently the instantaneous opening of the switch take place.

Such an arrangement does not at all fulfill the practical requirements, specially as it, ensures merely a protection against overloadings at the failing of the current in one phase, but not against the sudden strong excess current occuring at short circuiting or against heating by low net voltage.

Protecting switches have already been pro posed, which are designed to render inefi'ective these disturbances, but these switches do not give satisfaction as, owing to thermically acting releasing, they ought to function merely at inadmissible heating so that consequently the motor to be protected took up at first the occurring excess currents and was cut-off only when the admissible heatinglimit was reached.

There has further become known an independent switch for multiphase installations, in which one solenoid is inserted in each phase-wire, the cores of all these 'solenoids acting upon a common movable bridge which operates the spring-closure oi: the switch-elements. The cores of the solenoids are directly hinged to the ends of the bridge which has several arms, while the bridge itself is supported at its centre through the intermediary of a ball-joint by a spring-controlled member, and pressed on the opposite side against the abutment of the locking hook, arranged on the switch-handle. This solution of the transmission of the movement of the solenoid-cores upon the switch-bridge is a consequence of the utilization of solenoids and makes impossible an accurate and uniform functioning of the protecting switch, so that not only excess currents can really flow temporarily to the element to be protected, but in general the absolutely necessary security of the arrangement is not ensured.

In comparison herewith the invention consists in a protecting switch for multiphasecurrent-nets, in which for each phase one electromagnet is arranged through which the current flows and in which an automatic interruption of the net circuit is efiected as well when the current fails as when excess current occurs, but for this switch the combination of the following characteristic features is essential.

Each electromagnet acts upon at least two armatures, oscillatably mounted on the magnet-body of the electro-magnet, one of said armatures being attracted with adjustable retardation depending of the duration or strength of the magnet-excitation when a predetermined strength of current is being exceeded, whilethe other armature is permanently in contact with the magnet-body at a flow of current of any strength and drops OK as soon as the current ceases. The armatures of all the electromagnets efi'ect, each one for itself, at each movement by mechanical or electromagnetic means, the opening of a switch bridge common to the phase-contacts, so that excess currents cannot get at the element to be protected.

By experiments with such switches it has been ascertained, that they do not in any case allow excess currents getting at the element to be protected.

The use of electro-magnets, in which one coil-operates with two armatures the one of which is held attracted at flow ot current ofa certain voltage and drops off only, when the voltage descends under a certain currentstrength, while the other armature is at: tracted at the occurrence of the abnormal current-strength, has become known from maximum and minimum switches for .continuous currents. The invention relates, however, to a multiphase current protecting switch and just in such a switch the utilization of electromagnets of the kind mentioned causes a number of advantages from which noids. The current-consumption of the coils.

can be reduced further and their resistance against short-circuiting can be considerably increased, as the armature which at currentflow is permanently in contact, can maintain permanently closed a portion of the ironpath, i. e. the magnetic path by being in con tact with the iron-core and as has been proposed in accordance with the further development of the invention.

A very im ortant consequence of the arrangement of the electromagnets with oscillatable armatures in the manner proposed is further, that the closing of the contacts of the phase-switch can be absolutely prevented as soon as disturbance exists in the net, for instance a short circuit.

Two connection arrangements for three phase motors and further constructional details of the switch are shown, by way of exof the control element.

- minate in a motor M an As shown in Fig. 1 the net work leads are ample, in the accompanying drawings in who Fig. 1 shows a connection diagram. Fig. 2 shows the control element.

Fig. 3 shows a second connection diagram. Fig. 4 shows a second form of construction Figs. 5-9 show each one of the various forms of construction of the electro-magnet with the corresponding armatures.

In all figures of the drawing I, II, III are the lines for the three bases which terpass through the phase switching contacts SI, SII, SIII.

connected to form the windings of electromagnets EI, EII, EIII which are subsequently excitedby the phase current.

The movable contacts of the switches SI,

' I $11, $111 are mechanically connectedto one another by a bridge a. This bridge forms the armature of an electromagnet b the coil 0 of which is in shunt withthe phase leads I and III. The supply wire for these windings passes through six series connected contact; to (1, so that, when one of these contact; is being interrupted, the exciting winding for the magnet b is instantaneously cut out so that this electromagnet isrnot energized.

The cores of the electromagnets EI, EII EIII are, with the exception of the form 0 construction shown inFigs. 6 and 9, of double T shape. Armatures c and e respective ly are pivotally connected tothe correspond-.

ing sides respectively of the lower lead positions of the T-shaped cores as shown in Fig. 9

1, so that their'free ends are controlled by 1 the effect of the magnetizing current and may be attracted towards the core. The free ends;

of the armatures 6 and e, cooperate with a contact element of the contacts d to d, in such a manner that when the armatures (2,,

e oscillate in one direction, each armature carries the assoclated extendedcontact element, and this interrupts consequently the corresponding contacts d to (i The armatures e and e, are also controlled by tension springs f and respectively the tension of the spring f,

a slide g which moves over a graduated scale 11 arranged opposite to its guide It. 1 Fig. 2 shows further that the armature e may act upon a rod k mounted on the core of the electro-magnet E1 in such a mannal direction against the action of a spring j the end I of said rod it being appropriately shaped and adapted to act upon a second rod n which can be shifted in a vertical direction against the action of a spring m, the lower v mg regulated in the manner shown in Fig. 2 by adjusting ner that said rod can be shifted in longitudil end 0 of this rodn resting upon the movable element of the contact d A pressure rod p fixed onthe armature 6 also acts on this element. f

Theelectro-magnets E11 and EIII are fitted in a similar manner as shown in Fig. 1. The armature e is slightly biased towards the leftv byits spring f so that the slightest current flowing through the electromagnet E1 is suflicient to maintain the armature attracted. If this flow of current is interrupted which happens for example taking place for instance when the current in one'phase fails, the armature which is coordinated to this phase drops instantaneously and breaks the circuit for the holding electro-magnet b. The right armature e, is designed to act at excess currents of different strengths by adjusting the spring and this armature c is attracted only when the el'ec-, tromagnet ET is excited accordingly.

This

attraction-takes place without any lag in stantaneously when the predetermined excess currentis attained. In the arrangement shown in Fig. 2 when the'armature e,

is attracted, it shifts the rod h to the left whereby the rod/n is depressed against the action of the spring m, the contact (1 being thus interrupted. The circuit through the der 8 filled for instance electro-magnet b isinterrupted at the same time, the bridge a is released and the contacts SI, bII, SIII are interrupted and the motor is stopped. The releasing of the bridge is efi'ected by means of springs F or the like. The flow of current through the electromagnets EI, EII, EIII, ceases at the same time so that the armatures 6 of all the electromagnets fall away from their respective cores. Even if the main switch is closed no current could flow through the electro-magnets 6 so that the switch will automatically open every time.

In the form of construction shown in Fig. 3 a third armature e is arranged in addition to the two armatures e and e a piston r beingconnected, by means of a rod 9 to the free end of said armature and moving in a cylinwith oil. In the cylinder wall holes 6 are arranged close to the position of rest of the piston, oil flowing through these holes 6 from the oil bath in which the whole switch is arranged, into said cylinder and inversely oil flows out from the cylinder back into the oil bath. The front end of the cylinder is closed by a cover plate having perforations and being adapted to be more or less uncovered by a slide. At the forward stroke of the piston r the oil flows at first rapidly out through the holes 5 until the piston has moved beyond these holes, the movement of the piston being then braked by the throttling through the holes in the cover late. p In this case the armature 6 operates, as described above. The armature 6, acts at heavy overloadings, for instance at short circuiting, instantaneously, whilst the armature e acts in a similar manner to the armature e upon the movable element of the contact d but only after overloading has continued .for a long time. In this construction three armatures are provided each acting in a different manner, said three armatures being provided for each row of electro-magnets EI, EII, EIII.

The armatures may be arranged in the manner shown in Fig. 5, and as shown in the diagram Fig. 3, on the core of the electro-magnet.

As shown in Fig. 7 and the plan view thereof Fig. 8, the armatures are all hinged to one member at three sides thereof.

It is advisable to select armatures of such a form of construction that the one iron-path is composed of two or'more portions. The

' double T -shape shown in Fi s. 4, 5 and 7 is for instance adapted for t is purpose in which the iron-path 'subdivides into the branches A and B (Figs. 4 and 5). The branch B is maintained permanently closed at a flow of current of any strength, as the armature e (Fig. 4) is in this case constantly in contact with the magnet, whereby a considerable reduction of current-consumption and increasing of the resistance of the coil against short-circuiting are obtained proved.

The open portion A of the iron-core is of such dimension that at current-increase attracting of the other armature 6,, or this armature e and the armature 6, takes place.

Fig. 9 shows another form of construction, in which the electromagnets consist of two separate cores, two armatures being fixed to one core and the third armature being arranged alone on the other core. I

Fig. 4 shows a construction of the control element and associated parts, in which the movement of the armatures 6 e and e are transmitted by mechanism comprising a rod t hingedly connected to the free ends of said armatures being adapted to act upon a pawl o pivotally mounted and controlled by a compression spring u. The pawl 01 has a nose w designed to co-operate with a counter-nose of a rod 00, mounted on the switch bridge a and of the main three phase switch adapted to be operated by means of a handle 3 through the intermediary of a two armed lever z.

When any one of the armatures e 6,, e

main switch is disengaged. The handle 1 is employed for rein-serting the main switch and the pawl device is thereupon brought into its inoperative position.

I claim 1. A multiphase protective system, comprising, in combination with a device to be protected several supply conductors each conductor comprising a first switch, a coil between said device to be protected and said first switch, a switch bridge common to all said first switchesincluding an electromagnet, the coil of said electromagnet for said switch bridge in shunt with two of said supply conductors, the armature of said electroma et being combined with said switch bri ge, a second switch in the circuit of said coil of said electromagnet, a low-current armature and an overload armature associated with each of said coils in said conductors each of said low-current armatures adapted to be held constantly attracted during the flow of current through its coil and adapted to drop upon failure of current and to open the corresponding second switch, each of" said overload armatures adapted to be attracted upon a predetermined current strength being exceeded and to open the corresponding second switch, and for throwing sai switch bridge in ofi' position upon deenergizing of said electromagnet by the open ing of said second switch.

2. A multiphase protective system, comprising in combination with a device to be protected, several supply conductors, each conductor comprisinga first switch and a coil between said device to be rotected and said first switch, a switch bri ge common to all said first switches, an electromagnet for said switch bridge the coil of said electromagnet in shunt with two of said conductors the armature of I said electromagnet combined with said switch bridge, a second switch in the circuit of the coil of said electromagnet, a low-current armature and a pair. of overload armatures associated with each of said .coils in said conductors, each of said lowcurrent armatures adapted to be held constantly attracted durin the flow'of current through its coil and adapted to drop upon failure of current to open said second switch, each of said overload armatures adapted to be attracted upon a predetermined current strength being exceeded and to open said second switch, means for throwing said switch bridge into ofl position upon deenergizing of its electromagnet by the opening of said second switch, and an 011 brake for each of said overload armatures for introducing a time lag to render the action of one armature of each pair of overload armatures dependent also upon the time interval during which the maximum safe current is exceeded.

3. A multiphase protective system comprising in combination with a device to be protected, several supply conductors comprising each a switch, an electromagnet, a

low-current armature adapted to be constant- 1 attracted by its electromagnet during the flbw of current of any strength and a pair of overload armatures adapted to be attracted by their electromagnet upon a predetermined current strength being exceeded, a fluid brake adapted to retard the attraction movement of the corresponding pair of overload armatures to render their action dependent also upon the time interval during which the maximum safe current is exceeded, a switch bridge common to all said switches and means for throwing said switch bridge into ofi position, the low-current armatures and the oyerload armatures of all said electromagnets commonly controlling said throwi-ig-oif means, this control performed by the movement of any one of said low-current armatures upon failure of current in one of said conductors or by the attraction of any one of said overload armatures upon the predetermined strength of current being exceeded in one conductor.

4. In a multiphase protective device as s ecified in claim 2, the time lag deviceconsisting of a fluid brake. 4

5, A multiphase protective system, comprising in combination with the device to be protected, several supply conductors comprising each a switch, a coil arranged between said device to be protected and said first switch, a switch bri ge common to all said first switches, an electromagnet for said switch bridge the coil of said lectromagnet in shunt with two of'said supply conductors, the armature of said electro-magnet combined with said switchbridge, a low-current armature and a pair of overload armatures associated with each of said coils in said supply conductors, each of said low current armatures adapted to be held constantly attracted during the flow of current through its coil, a second switch associated with each of said low current armatures, each of said overload armatures adapted tobe attracted upon a predetermined current strength being exceeded, a third switch associated with each of said pairs of overload armatures said second and said third switches connected in se ries and arranged in the circuit of the coil of the said electromagnet, means for throwing said switch bridge into oil-position upon deenergizing of said electromagnet, and an oil brake for each of said overload armatures for introducing a time lag to render the acti'on of said overload armature dependent also upon the time interval during which the maximum safe current is exceeded,

6. A multiple protective system, comprising in combination with the device to be protected, several supply conductors comprising each a switch, a coil between said device to- ,be protected and said first switch, an electro magnet the coil of said electromagnet in shunt with two of said supply conductors, a low-current armature constantly attracted by one of said coils during the flow of current of any strength, and an overload armature adapted to be attracted by one of said coils upon a predetermined current strenth being exceeded, a switch bridge common to the switches of all said supply conductors and controlled by said electro-magnet, means for throwing said switch bridge into ofi position the low-current armatures and the overload armatures of the coils of all of said supply conductors commonly controlling said thro'wing-ofi means by controlling the circuit to said electromagnet this control being performed by the movement of any one of said low-current. armatures upon failure of current in one of said conductors or by the attraction of any one of said overload armatures .upon the predetermined, strength of current being exceeded in one of said conductors, a second overload armature for each of-said electromagnets, an oil brake for each of said second overload armatures for introducing a time lag to render the action of the corresponding second overload-armature not only dependent.

upon the strength of current but also upon the time interval during which the maximum safe current is exceeded said second overload armature also'acting upon said throwing ofi means. I

tected, several supply conductors 7. A multiple protective system, comprising in combination with the device to be protected, several supply conductors comprising each a switch, a coil between said device to be protected and said first switch, an electromagnet the coil of said electro magnet in shunt with two. of said supply conductors, a low current armature constantly attracted by one of said coils during the flow of current of any strength, and an overload armature adapted to be attracted by one of said coils upon a predetermined current strength being exceeded, a switch bridge common to the switches of all said supply conductors and controlled by, said electro-magnet for throwing said switch bridge into ofi position, the low current armatures and the overload armatures of the coils of all of said supply conductors commonly controlling said throwing oflz' means by controlling the circuit of said electro-magnet, this control being performed by the movement of any one of said low-current armatures upon failureof current in one of said conductors or by the attraction of any one of said overload armatures upon the predetermined strength of current being exceeded in one of said conductors.

8. A multiple protective system,

comprismg in combination with the device to be procomprising each a switch, a coil between said device to be protected and said first switch, an electromagnet the coil of said electro-magnet in shunt with two of said supply conductors. a low current armature constantly attracted by one of said coils during the flow of current of any strength, and an overload armature adapted to be attracted by one of said coils upon a predetermined current strength being exceeded, means for introducing a time lag to render the action of the corresponding overload-armature not only dependent upon the strength of current but also upon the time interval during which the maximum safe current is exceeded, a switch bridge common to the switches of all said supply conductors and controlled by said electromagnet, means for throwing said switch bridge into ofi position the low-current armatures and the overload armatures of the coils of all of said supply conductors commonly controlling said throwing 01f means by controlling the circuit of said electromagnet, this control being performed by the movement of any one of said low-current armatures upon failure of current in one of said conductors or by the attraction of any one of said overload armatures upon the predetermined strength of current being exceeded in one of said conductors.

In testimony whereof I aifix my signature.

GEORG KELLER. 

